New Delhi: Air pollution due to crop residue burning in northern India causes an estimated economic loss of USD 30 billion annually, and is a leading risk factor of acute respiratory infections, especially among children, according to a study unveiled Monday.

Researchers from the US-based International Food Policy Research Institute (IFPRI) and partner institutes found that living in districts with air pollution from intense crop residue burning (CRB) is a leading risk factor for acute respiratory infection (ARI), particularly in children less than five years of age.

The study that estimates -- for the first time -- the health and economic costs of CRB in northern India also found that CRB leads to an estimated economic loss of over USD 30 billion annually.

"Poor air quality is a recognised global public health epidemic, with levels of airborne particulate matter in Delhi spiking to 20 times the World Health Organization's safety threshold during certain days," said Samuel Scott, IFPRI Research Fellow and co-author of the study.

"Among other factors, smoke from the burning of agricultural crop residue by farmers in Haryana and Punjab especially contributes to Delhi's poor air, increasing the risk of ARI three-fold for those living in districts with intense crop burning," Scott said in a statement.

The study also estimated the economic cost of exposure to air pollution from crop residue burning at USD 30 billion or nearly Rs 2 lakh crore annually for the three north Indian states of Punjab, Haryana and Delhi, researchers said.

To be published in the upcoming edition of the International Journal of Epidemiology, the study analysed health data from more than 250,000 individuals of all ages residing in rural and urban areas in India.

It used NASA satellite data on fire activity to estimate the health impact of living in areas with intense crop burning by comparing them with areas not affected by CRB.

The researchers observed that as crop burning increased in the northern Indian state of Haryana, respiratory health worsened. Health was measured by the frequency of reported hospital visits for ARI symptoms.

They also examined other factors that could contribute to poor respiratory health such as firecracker burning during Diwali (it usually coincides with time of CRB) and motor vehicle density.

Economic losses owing to exposure to air pollution from firecracker burning are estimated to be around USD 7 billion or nearly Rs 50 thousand crore a year, researchers said.

In five years, the economic loss due to burning of crop residue and firecrackers is estimated to be USD 190 billion, or nearly 1.7 per cent of India's gross domestic product (GDP), they said.

"Severe air pollution during winter months in northern India has led to a public health emergency. Crop burning will add to pollution and increase healthcare costs over time if immediate steps are not taken to reverse the situation," said Suman Chakrabarti from the University of Washington in the US.

The negative health effects of crop burning will also lower the productivity of residents and may lead to long-term adverse impacts on the economy and health," Chakrabarti said in a statement.

"Our study shows that it is not only the residents of Delhi, but also the women, children and men of rural Haryana who are the first victims of crop residue burning," added Avinash Kishore from IFPRI.

"Much of the public discussion on ill-effects of crop residue burning ignores this immediately affected vulnerable population," said Kishore.

Even though air pollution has been linked to numerous health outcomes, and respiratory infections are a leading cause of death and disease in developing countries, none of the existing studies have directly linked crop burning to ARI.

This study suggests that targeted government initiatives to improve crop disposal practices are worthy investments, researchers said.

"Programmes and policies must simultaneously address indoor and outdoor pollution through a possible combination of bans and agricultural subsidies.

"Other important interventions for improving respiratory health are increasing household access to clean cooking fuels, electricity, and improved drainage systems," Kishore added.

Researchers noted that crop burning is a widespread global practice and in India is concentrated in northwest India, though has spread to other regions of the country in the past decade as new crop harvesting technology is adopted.

Farmers try to maximise their yields by planting the next crop as soon as possible after the previous crop has been harvested (generally wheat after rice).

To quickly clear the field for the next crop, they burn the leftover stubble rather than using the traditional method of clearing it by hand.